The present invention relates to a cable connector which electrically connects with an electromagnetic wave shielded cable generally for use in various electronic equipment including communication equipment such as an electronic automatic exchange, an electronic transmission equipment or the like and computer equipment. In detail, the present invention relates to a cable connector which has a ground plate between the cable connector and a mating connector to form a shield-ground path from the cable to the ground plate so as to drop external electromagnetic wave noise mixed in from the electromagnetic wave shielded cable. In more detail, the present invention relates to a cable connector forming a shield-ground path by bringing conductive electrical contacts provided on the cable connector into elastic contact with the ground plate when the connector is fit-connected. The present invention also relates to a connector system including the cable connector and communication equipment using the connector system.
An electronic automatic exchange houses, for example, a plurality of exchange units in its cabinet. The exchange unit is provided with a printed circuit board having a printed circuit board (PCB) connector in its casing. The casing of the exchange unit is conductive and this conductive casing electromagnetically shields the printed circuit board. Part of the conductive casing is used as a ground plate by grounding this part. A cable connector electrically connected to the electromagnetic wave shielded cable is used to electrically connect PCB connectors in the same electronic automatic exchange to each other or PCB connectors in separate electronic automatic exchanges to each other.
FIG. 1 shows how a cable connector 111 connected to a shielded cable 119 is fit-connected to a PCB connector 103 via a ground plate 101 of an exchange unit. The PCB connector 103 is constituted by an insulator 107 holding male contacts 105 placed in its inner space. On the other hand, the cable connector 111 is provided with female contacts 115 which electrically connect to signal lines 121 of the cable 119 and the respective male contacts 105 of the PCB connector 103, a contact housing 117 for housing the female contacts 115, a shield shell having conductivity (not shown), an insulating cover 118 for enclosing the shield shell and electrical contacts 113 which extend from the shield shell and are exposed from a gap between the contact housing 117 and the insulating cover 118.
The cable 119 is constituted such that a plurality of signal lines 121 are enclosed with a jacket shield. These signal lines 121 are electrically connected to the respective female contacts 115 while the jacket shield is electrically connected to the shield shell of the cable connector 111. When the connector is fit-connected, a shield-ground path is formed from the cable 119 to the ground plate 101 since electrical connection is secured by bringing the electrical contact 113 into elastic contact with the conductive ground plate 101.
However, the electrical contacts 113 shown in FIG. 1 are of a cantilever type, in which a plate spring is straight. Since the spring length from a supported end (fulcrum of the spring) held by the shield shell to a contact end, which is an action point, is short in the electrical contact 113 having a straight plate spring, the spring generates greater displacement in relation to a load (so called rigid spring having a large spring constant value). As a result, a spring displacement region required for obtaining a sufficient contact force inevitably becomes small. When a distance between the electrical contact 113 and the ground plate 101 is increased due to poor location accuracy of the ground plate 101 in relation to the cable connector 111, variation in protrusion levels of the contact ends of the electrical contacts 113 and so forth, the contact of the electrical contacts 113 to the ground plate 101 is deteriorated (sufficient spring force cannot be secured). Therefore, a problem arises that impedance of the shield-ground path is increased, thereby resulting in decline of the shield ground effect.
Accordingly, an object of the present invention is to provide a cable connector in which a shield-ground path from a shielded cable to a ground plate has low impedance when a cable connector connected to the shielded cable is fit-connected to a mating connector via the ground plate. Another object of the present invention is to provide a connector system including this cable connector and communication equipment using this connector system.
To achieve the above objects, the present invention provides a cable connector which electrically connects to a shielded cable containing signal lines shielded with a jacket shield and is fit-connected to a mating connector via a ground plate. This cable connector is provided with a contact housing including first contacts electrically connected to signal lines, a shield shell which electrically connects to the jacket shield and covers the contact housing and an insulating cover for covering the shield shell. The cable connector has electrical contacts which are composed of generally U-like bent plate springs supported at one ends on the shield shell and come into elastic contact with the ground plate when the cable connector is fit into a mating connector.
The cable connector having the above constitution, on a surface opposed to the mating connector, has electrical contacts which are composed of generally U-like bent plate springs supported at one ends on the shield shell and come into elastic contact with the ground plate when the cable connector is fit into the mating connector. That is, the bent plate spring typically has a generally U-like shape, but those bent into a generally V-like shape, a generally W-like shape, a generally bellows-like shape and the like are also encompassed. An end portion on the cable side of the generally U-like bent plate spring is fixed and supported on the shield shell.
In case of a generally U-like bent plate spring, when one U-like end on the cable side (first supported end) is fixed and supported on the shield shell, the end fixed and supported on the shield shell becomes a fulcrum of the spring while the U-like bent site becomes an action point of the spring. Furthermore, this bent site also becomes a fulcrum for the other end having a U-like shape (end portion on the mating connector side). The other end on the mating connector side becomes a final action point. In a generally U-Like bent plate spring, one end on the cable side becomes a fulcrum of a spring and the other end on the mating connector side becomes the final action point. The whole length of the generally U-like plate spring serves as the spring length. Thus, since the length of a bent type spring can be made longer spring than a straight spring, the spring constant of the plate spring can be reduced as compared with that of a conventional straight spring. As a result, a large spring displacement region required for obtaining a necessary and sufficient contact force can be secured. Therefore, since stable contact (force) can be obtained between the plate springs and the ground plate, electrical connectability of the electrical contacts to the ground plate is improved and the shield-ground path from the shielded cable to the ground plate has low impedance.
The electrical contact preferably extends from an end portion of the bent plate spring on the cable side in a fitting direction of the connector on the cable side and has a supported portion held by the shield shell. According to such a constitution, the end portion of the bent plate spring on the cable side is fixed and supported at the supported portion held by the shield shell. Since the supported portion can resist the elastic force acted when the bent plate spring comes into contact with the ground plate, supporting property of the electrical contact is improved and thereby stable contact can be obtained. Therefore, electrical connectability of the electrical contacts to the ground plate is improved.
The supported portion of the electrical contact can also be constituted so as to be held at its part by the shield shell. In the supported portion of this constitution, the end portion on the bent plate spring side of the part held by the shield shell serves as a fulcrum of the spring and the part not held by the shield shell becomes a spring action part That is, in addition to the bent plate spring, the part not held by the shield shell acts as a spring. Therefore, the spring length of the electrical contact is made further longer than when substantially whole the supported portion is held by the shield shell. Therefore, since the spring constant of the plate spring can be reduced, further stable contact with the ground plate can be obtained on the basis of the aforementioned theory. Thus, electrical connectability of the electrical contacts to the ground plate is further improved.
The electrical contacts are preferably used as at least one pair. According to such a constitution, even if there is a displacement in a connector fitting direction between the electrical contacts and the ground plate, either of the electrical contacts absorbs the displacement. Therefore, stable contact can be obtained. Thus, electrical connectability of the electrical contacts to the ground plate is improved.
Preferably, the electrical contacts are formed integrally with the shield shell. A portion to be processed which has a shape corresponding to the electrical contact is provided on the shield shell in advance. The portion to be processed is subjected to processing such as folding or the like to form an electrical contact in a predetermined shape. Therefore, as compared with the case where separately formed electrical contacts are attached to the shield shell afterwards, the number of components and the number of manufacturing processes are reduced, thereby resulting in reduced costs.
In a connector system in which a ground plate is arranged between the cable connector and the mating connector, a shield-ground path is formed therebetween when the cable connector is fit-connected to the mating connector since the electrical contacts of the cable connector come into elastic contact with the ground plate. In this connector system, the electrical contacts come into stable contact with the ground plate by a necessary and sufficient spring force with the same reason as described above about the cable connector. Therefore, a shield-ground path having low impedance can be formed and external electromagnetic wave noise can be reduced.
The PCB connector as the mating connector and the cable connector are applied in communication equipment provided with a plurality of units having printed circuit boards in a box-like conductive casing. That is, in this communication equipment, part of the conductive casing for the units is grounded and used as a ground plate. A constitution is obtained that the ground plate is arranged between the PCB connector provided on the printed circuit board and the cable connector having the electrical contacts. In the communication equipment having such a constitution, when the cable connector is fit-connected to the PCB connector, the electrical contacts come into stable contact with the ground plate with the same reason as described above about the connector system. Therefore, the printed circuit boards housed in respective units can be connected by a shield-ground path having low impedance and external electromagnetic wave noise mixed in can be reduced.